Fully passive third-order noise shaping SAR ADC.

In this Letter, an opamp-free noise shaping successive-approximation register (SAR) ADC is proposed. Third-order noise shaping is achieved by implementing a second-order passive filter and a passive error feedback topology. In the proposed scheme, the SAR error signals (including quantisation noise, comparator thermal noise, DAC thermal noise and settling error) are subjected to third-order noise shaping. Therefore, the thermal noise specifications of the comparator can be relaxed. Also, since no active element is used, the proposed scheme achieves a higher power efficiency than earlier SAR ADCs. [ABSTRACT FROM AUTHOR]